//代码块复制按钮
.highlight{
  //方便copy代码按钮（btn-copy）的定位
  position: relative;
}
.btn-copy {
  display: inline-block;
  cursor: pointer;
  background-color: #eee;
  background-image: linear-gradient(#fcfcfc,#eee);
  border: 1px solid #d5d5d5;
  border-radius: 3px;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
  -webkit-appearance: none;
  font-size: 13px;
  font-weight: 700;
  line-height: 20px;
  color: #333;
  -webkit-transition: opacity .3s ease-in-out;
  -o-transition: opacity .3s ease-in-out;
  transition: opacity .3s ease-in-out;
  padding: 2px 6px;
  position: absolute;
  right: 5px;
  top: 5px;
  opacity: 0;
}
.btn-copy span {
  margin-left: 5px;
}
.highlight:hover .btn-copy{
  opacity: 1;
}
